1. Field of the Invention
This invention relates generally to metal cutting tools and, more particularly, to face milling cutters having indexable inserts mounted thereon.
2. Description of the Prior Art
Known milling cutters used for difficult to machine materials, such as alloys of titanium, typically have employed cutting edges exhibiting high positive geomerty--i.e. relatively large positive axial and radial rake angles. Such designs have shown tendencies of relatively short cutting edge life and the necessity of using large numbers of cutting inserts at relatively low feed rates for face milling operations.
One known cutter designed for taking relatively shallow cuts in materials such as titanium is described in my prior U.S. Pat. No. 4,194,860, assigned to the same assignee as the instant invention. The face mill of this prior patent, while demonstrating outstanding results in its intended application, is not capable of taking deep cuts in the range of 0.2"-0.4", due to the unique geometrical insert positioning employed.
Other milling cutters using so-called "on-edge" insert positioning are known. On-edge configurations feature mounting of a cutting insert to place a major dimension or depth of insert material behind the insert's cutting edges to better absorb cutting forces placed on the insert. With this arrangement, inserts may typically be mounted to a cutter body with relatively simple screw-down designs, avoiding the necessity for shims, wedges, or other special insert mounting and clamping hardware.
One example of a prior on-edge cutter, in addition to the cutter disclosed in my prior patent discussed above, is shown in U.S. Pat. No. 3,818,562--Lacey. However, this patent uses relatively extreme negative radial rake for the cutting edges of its disclosed cutter. Such geometry has traditionally been found deficient in cutting efficiency for applications involving difficult to machine materials such as alloys of titanium.
One prior art disclosure that superficially resembles a design capable of using the cutting edge geometry taught herein is found in U.S. Pat. No. 3,716,900--Erkfritz. However, this patent teaches cutting inserts of very complex shape with consequent high manufacturing cost. Additionally, the Erkfritz patent teaches use of relatively complex required mounting hardware.
Therefore, there is seen to be a need for a relatively simple, hence economical, face mill for taking large depths of cut in hard to machine materials such as titanium alloys.